Human skin pigmentation as an adaptation to UV radiation

Bibliographic Data

ID23337896
AuthorsNina G Jablonski (Department of Anthropology, Pennsylvania State University, University Park, PA 16802), Nina Jablonski (0000-0001-7644-874X, Department of Anthropology, Pennsylvania State University, University Park, PA 16802), George Chaplin (0000-0002-7341-7742, Department of Anthropology, Pennsylvania State University, University Park, PA 16802)
Year2010
Volume107
Issuesupplement_2
Pages8962-8968
Publication date2010-05-11
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueProceedings of the National Academy of Sciences (JOURNAL)
Journal identifiersISSN: 0027-8424 • E-ISSN: 1091-6490
PublisherNational Academy of Sciences (PUBLISHER • US)
DOI10.1073/pnas.0914628107
PMID20445093
PMCIDPMC3024016
OpenAlexW2127501217
LanguageEN
Citations received63
References cited72

Human skin pigmentation is the product of two clines produced by natural selection to adjust levels of constitutive pigmentation to levels of UV radiation (UVR). One cline was generated by high UVR near the equator and led to the evolution of dark, photoprotective, eumelanin-rich pigmentation. The other was produced by the requirement for UVB photons to sustain cutaneous photosynthesis of vitamin D 3 in low-UVB environments, and resulted in the evolution of depigmented skin. As hominins dispersed outside of the tropics, they experienced different intensities and seasonal mixtures of UVA and UVB. Extreme UVA throughout the year and two equinoctial peaks of UVB prevail within the tropics. Under these conditions, the primary selective pressure was to protect folate by maintaining dark pigmentation. Photolysis of folate and its main serum form of 5-methylhydrofolate is caused by UVR and by reactive oxygen species generated by UVA. Competition for folate between the needs for cell division, DNA repair, and melanogenesis is severe under stressful, high-UVR conditions and is exacerbated by dietary insufficiency. Outside of tropical latitudes, UVB levels are generally low and peak only once during the year. The populations exhibiting maximally depigmented skin are those inhabiting environments with the lowest annual and summer peak levels of UVB. Development of facultative pigmentation (tanning) was important to populations settling between roughly 23° and 46° , where levels of UVB varied strongly according to season. Depigmented and tannable skin evolved numerous times in hominin evolution via independent genetic pathways under positive selection.

Adaptation (eye) · Biology · Botany · Evolutionary biology · Facultative · Human skin · Natural selection · Photoprotection · Photosynthesis · Population · Acne and Rosacea Treatments and Effects · Genetics · Medicine · melanin and skin pigmentation · Skin Protection and Aging